The present invention relates to an optical transmitter/receiver apparatus with integrated hybrid functions of optical reception and transmission for use in optical fiber communication for transmitting an optical signal, which has been output from a semiconductor laser device, through an optical fiber, and also relates to a method for fabricating the same. The present invention further relates to an optical semiconductor module formed by optically coupling a semiconductor laser device to an optical fiber.
In recent years, a fiber-to-the-user system for transmitting data and multi-channel image information from a center station to a home user by using an optical fiber has been pro posed and the implementation of such a system is now under consideration. Such a fiber-to-the-user system requires a plurality of optical receiver apparatuses for simultaneously receiving dissimilar optical signals transmitted by wavelength division multiplexing to the terminal device of a home user and an optical transmitter apparatus for transmitting requests, data and the like from the user""s terminal device to the center station.
In an optical transmitter apparatus or optical receiver apparatus used for a fiber-to-the-user system, various types of passive alignment mounting techniques are often employed for the purposes of coupling the apparatus to an optical fiber without operating a light-emitting device or a light-receiving device and thereby reducing the costs thereof.
In order to further reduce the size of such an apparatus and further enhance the performance thereof, technology for integrating optical receiver apparatus and optical transmitter apparatus in a compact package is now in great demand.
In response to such demand, an optical transmitter/receiver apparatus, in which an optical receiver apparatus and an optical transmitter apparatus are integrated in a compact package as shown in FIGS. 37(a) and 37(b), has been suggested (see, for example, 1996 Annual Convention of Institute of Electronics, Information and Communication Engineers in Japan, SC-2-5).
Hereinafter, the conventional optical transmitter/receiver apparatus will be described with reference to FIGS. 37(a) and 37(b).
FIG. 37(a) shows a planar structure of the conventional optical transmitter/receiver apparatus, while FIG. 37(b) shows the cross-sectional structure thereof taken along the line Axe2x80x94A of FIG. 37(a). The conventional optical transmitter/receiver apparatus includes a fiber block 10 and a PLC (planar lightwave circuit) substrate 20 that are joined with each other. The fiber block 10 supports one end of a first optical fiber 11 for transmitting/receiving an optical signal therethrough and one end of a second optical fiber 12 for receiving an optical signal therethrough. On the other hand, the PLC substrate 20 supports: a semiconductor laser device 21 for outputting light on a wavelength band of 1.3 xcexcm; a monitoring light-receiving device 22 for monitoring the output of the semiconductor laser device 21; a first lightreceiving device 23 for signal reception for receiving light on the wavelength band of 1.3 xcexcm; and a WDM (wavelength division multiplexed) filter 24 for transmitting light on the wavelength band of 1.55 xcexcm and reflecting light on the wavelength band of 1.3 xcexcm. An optical waveguide 25 is formed inside the PLC substrate 20. A second light-receiving device 13 for signal reception for receiving light on the wavelength band of 1.55 xcexcm and outputting image information is connected to the other end of the second optical fiber 12 for reception.
The fiber block 10 and the PLC substrate 20 are optically coupled to each other at an output port 26 and a common port 27. The light to be transmitted on the wavelength band of 1.3 xcexcm, which has been output from the semiconductor laser device 21, is passed through a Y-shaped branch 25a of the optical waveguide 25, the WDM filter 24 and the common port 27 so as to be output through the other end of the first optical fiber 11. Light on the wavelength band of 1.3 xcexcm and light on the wavelength band of 1.55 xcexcm are input to be received through the other end of the first optical fiber 11. The former light, i.e., light on the wavelength band of 1.3 xcexcm, is passed through the common port 27, the WDM filter 24 and the Y-shaped branch 25a of the optical waveguide 25 so as to be received by the first light-receiving device 23. The latter light, i.e., light on the wavelength band of 1.55 xcexcm, is reflected by the WDM filter 24 and passed through the output port 26 so as to be received by the second light-receiving device 13.
In the conventional optical transmitter/receiver apparatus, the entire coupling, except for the coupling between the first and second optical fibers 11 and 12 (which are external transmission lines) and the PLC substrate 20, is realized by passive alignment.
The conventional optical transmitter/receiver apparatus shown in FIGS. 37(a) and 37(b) uses the PLC substrate 20 as an optical platform. However, if a PLC substrate 20 made of silica material is used, shortening of the length of the PLC substrate 20 is restricted by the minimum bend radius of the waveguide 25. Thus, since the PLC substrate 20 becomes rather long in the direction in which light travels, downsizing of such an optical transmitter/receiver apparatus is hard to realize. That is to say, the waveguide 25 of the PLC substrate 20 has a minimum bend radius, over which loss is caused because of difference in refractive indices between a waveguide layer and a cladding layer. If the difference between the refractive indices is increased, then the minimum bend radius can be decreased. However, in actuality, even when the difference between the refractive indices is increased up to 0.75% (which is the maximum value considering the internal loss of the waveguide and the loss resulting from the coupling with the optical fiber), the minimum bend radius cannot be decreased less than about 5 mm. Thus, in the optical transmitter/receiver apparatus shown in FIGS. 37(a) and 37(b), the required minimum length of the PLC substrate 20 in the optical axis direction is as long as about 15 mm. Since the optical transmitter/receiver apparatus further requires the fiber coupling portion, the resulting length of the apparatus in the optical axis direction becomes 20 mm or more.
Also, in the conventional optical transmitter/receiver apparatus, the light to be received on the wavelength band of 1.55 xcexcm, which has been input into the waveguide 25 of the PLC substrate 20, is output through the output port 26 of the PLC substrate 20 into the second optical fiber 12 and then received by the second light-receiving device 13. Accordingly, cost reduction and downsizing of the optical transmitter/receiver apparatus are adversely restricted.
During the assembly process of this apparatus, a cut recess is provided for the PLC substrate 20 by using a dicing saw, the WDM filter 24 is inserted into the recess, and position and angle of the WDM filter 24 are adjusted. However, since it is difficult to mount the WDM filter 24 with high accuracy, the loss of the light, which is incident through the common port 27 and then travels toward the output port 26, disadvantageously increases.
In addition, when the fiber block 10 is joined with the PLC substrate 20, the first optical fiber 11 and the second optical fiber 12 need to be simultaneously connected to the common port 27 and the output port 26 with high efficiency. Thus, since these parts should be aligned through active alignment, the assembly process is adversely complicated.
Furthermore, mounting process steps requiring high accuracy should be performed when the semiconductor laser device 21 is mounted onto the PLC substrate 20, when the first light-receiving device 23 is mounted onto the PLC substrate 20, when the monitoring light-receiving device 22 is located near the semiconductor laser device 21 and when the first and second optical fibers 11 and 12 are mounted into the PLC substrate 20. Since the number of process steps requiring high accuracy is large, cost reduction is difficult to realize.
In an optical semiconductor module used as an optical transmitter apparatus, a concave groove having a V-shaped cross section and extending in the optical axis direction is formed in a base made of silicon and an optical fiber is installed in the concave groove. In such a manner, the optical fiber can now be mounted on the base with high accuracy.
However, as for mounting of a semiconductor laser device, it is difficult to mount the semiconductor laser device onto the base with high accuracy. This is because electrodes are formed on the semiconductor laser device and the base and the size of the semiconductor laser device is small.
Thus, technology for accurately mounting a semiconductor laser device onto a base by passive alignment is now required. A method for fabricating an optical semiconductor module such as that shown in FIG. 38 is suggested by T. Hashimoto et al., MOC ""95, D5, 1995.
As shown in FIG. 38, a concave groove 31, extending in the optical axis direction, for positioning a fiber and a cut recess 32 extending vertically to the optical axis are formed. in a base 30 made of silicon. A wiring pattern 33 formed of an Au layer and base marks 34, formed of an Au layer, for alignment are also provided for the base 30. On the other hand, on the reverse surface of a semiconductor laser device 40, a surface electrode (not shown) formed of an Au layer and laser marks 41, formed of an Au layer, for alignment, are also formed. In such a case, the wiring pattern 33 and the base marks 34 of the base 30 are formed during the same process step. Similarly, the surface electrode and the laser marks 41 of the semiconductor laser device 40 are also formed during the same process step. Thus, no special processing is required for passive alignment.
The base 30 is aligned with the semiconductor laser device 40 by making a CCD camera 52 receive infrared rays 51, which have been emitted from an infrared light source 50 and then transmitted through the base 30 and the semiconductor laser device 40, and recognize the base marks 34 of the base 30 and the laser marks 41 of the semiconductor laser device 40 as images.
By installing a singlemode optical fiber 60 in the concave groove 31, the position of the fiber 60 on a plane vertical to the optical axis is determined. And when the fiber 60 comes into contact with a stopper wall of the cut recess 32 (i.e., a wall face closer to the semiconductor laser device 40), the position thereof in the optical axis direction is determined.
However, the conventional optical semiconductor module shown in FIG. 38 has the following problems.
First, a mask for forming the base marks 34 should be aligned with the concave groove 31 of the base 30 such that the base marks 34 and the concave groove 31 are located at the same position in the direction vertical to the optical axis on the plane parallel to the surface of the base 30. However, when the mask alignment is performed, the mask always deviates to some degree. As a result, some misalignment is always caused between the base marks 34 and the concave groove 31. Since the semiconductor laser device 40 is positioned by using the base marks 34 that are already out of alignment with the concave groove 31, the semiconductor laser device 40 is very likely to deviate twofold with respect to the concave groove 31.
In addition, when the CCD camera 52 receives the infrared rays 51 emitted from the infrared light source 50 and recognizes the marks as images, the CCD camera 52 simultaneously observes the base marks 34 and the laser marks 41, which are located away from the CCD camera 52 by mutually different distances. Thus, the image of either mark is adversely defocused and recognized as a blurred image.
The finer the base marks 34 and the laser mark 41 are, the more accurate and precise alignment is realized. However, since the base marks 34 and the laser mark 41 are formed through metal vapor deposition technique, the edges of the base marks 34 and the laser marks 41 are variable on the order of microns. Thus, the image recognition cannot be performed with satisfactorily high precision.
Furthermore, the relative distance between the emission end face of the semiconductor laser device 40 and the laser marks 41 is variable on the order of several microns depending upon the cleavage precision. In the same way, the relative distance between the stopper wall face of the cut recess 32 of the base 30 and the base mark 34 is also variable on the order of several microns depending upon the formation precision of the cut recess 32.
Moreover, according to the conventional image recognition method, mechanical adjustment is performed by recognizing the superposed pattern of the base marks 34 and the laser marks 41 as an image by the use of the infrared rays 51 emitted from the infrared light source 50. Thus, the conventional image recognition method cannot suppress the variation in the relative position between the emission end face and the laser marks 41 of the semiconductor laser device 40 and the variation in the position where the cut recess 32 of the base 30 is formed.
Because of the various problems described above, in the conventional optical semiconductor module, a large degree of misalignment is likely to be caused between the optical axis of the semiconductor laser device and the optical axis of the optical fiber and the distance between the emission end face of the semiconductor laser device and the incidence end face of the optical fiber is also variable to a large extent.
In view of the above-described conventional problems, a first object of the present invention is to accomplish cost reduction, downsizing and performance enhancement of an optical transmitter/receiver apparatus by providing a highly integrated optical transmitter/receiver apparatus that can be assembled easily. A second object of the present invention is to reduce the misalignment between the optical axes of a semiconductor laser device and an optical fiber and to suppress the variation in distance between the emission end face of the semiconductor laser device and the incidence end face of the optical fiber.
In order to accomplish the first object, a first optical transmitter/receiver apparatus of the present invention includes: an optical fiber for transmitting an optical signal to be transmitted and receiving an optical signal to be received therethrough; a first base including mutually spaced optical signal transmitting and receiving regions and a fiber end supporting region located between the optical signal transmitting and receiving regions; a semiconductor laser device, secured to the optical signal transmitting region of the first base, for emitting the optical signal to be transmitted; fiber end supporting means, formed in the fiber end supporting region of the first base, for supporting one end of the optical fiber, the optical signal to be transmitted that has been emitted from the semiconductor laser device being incident onto the end of the optical fiber; a second base, secured to the optical signal receiving region of the first base, for supporting the body of the optical fiber; a reflective filter, supported by being inserted into the second base and the body of the optical fiber, for transmitting the optical signal to be transmitted that has been emitted from the semiconductor laser device, and for reflecting the optical signal to be received that has been incident through the other end of the optical fiber; and a light-receiving device, secured to the second base, for receiving the optical signal to be received that has been reflected by the reflective filter.
In the first optical transmitter/receiver apparatus, the second base, supporting the body of the optical fiber, the light-receiving device and the reflective filter inserted into the body of the optical fiber, is secured to the first base, to which the semiconductor laser device has been secured and which supports one end of the optical fiber via the fiber end supporting means. Thus, it is possible to secure the second base to the first base after the second base supporting the body of the optical fiber, the light-receiving device and the reflective filter and the first base supporting the semiconductor laser device and the one end of the optical fiber have been separately formed. As a result, the assembly process can be simplified as compared with a structure in which semiconductor laser device, one end and body of an optical fiber, reflective filter and light-receiving device are all secured to a single base.
In the first optical transmitter/receiver apparatus, when the semiconductor laser device and one end of the optical fiber are secured to the first base, only the positional relationship therebetween should be considered. Similarly, when the reflective filter and the light-receiving device are secured to the second base, only the positional relationship therebetween should be considered. Thus, the semiconductor laser device and one end of the optical fiber can be secured easily, while accurately defining the positional relationship therebetween. In the same way, the reflective filter and the light-receiving device can also be secured easily, while accurately defining the positional relationship therebetween. Consequently, in the first optical transmitter/receiver apparatus, the optical axis can be adjusted on the order of submicrons through passive alignment.
In order to accomplish the first object, a second optical transmitter/receiver apparatus according to the present invention includes: a package; an optical fiber for transmitting an optical signal to be transmitted and receiving an optical signal to be received therethrough; a first base, being secured to a bottom of the package, including an optical signal transmitting region and an optical signal receiving region that are spaced from each other, and further including a fiber end supporting region located between the optical signal transmitting region and the optical signal receiving region; a semiconductor laser device, secured to the optical signal transmitting region of the first base, for emitting the optical signal to be transmitted; fiber end supporting means, formed in the fiber end supporting region of the first base, for supporting one end of the optical fiber, the optical signal to be transmitted that has been emitted from the semiconductor laser device being incident onto the end of the optical fiber; a second base, secured to the bottom of the package, for supporting a body of the optical fiber; a reflective filter, supported by being inserted into the second base and the body of the optical fiber, for transmitting the optical signal to be transmitted that has been emitted from the semiconductor laser device, and for reflecting the optical signal to be received that has been incident through the other end of the optical fiber; and a light-receiving device, secured to the second base, for receiving the optical signal to be received that has been reflected by the reflective filter.
In the second optical transmitter/receiver apparatus, it is possible to secure the second base to the package after the first base supporting the semiconductor laser device and the one end of the optical fiber and the second base supporting the body of the optical fiber, the reflective filter and the light-receiving device have been separately formed. As a result, the assembly process can be simplified as compared with a structure in which semiconductor laser device, one end and body of an optical fiber, reflective filter and light-receiving device are all secured to a single base.
In the second optical transmitter/receiver apparatus, when the semiconductor laser device and one end of the optical fiber are secured to the first base, only the positional relationship therebetween should be considered. Similarly, when the reflective filter and the light-receiving device are secured to the second base, only the positional relationship therebetween should be considered. Thus, the semiconductor laser device and one end of the optical fiber can be secured easily, while accurately defining the positional relationship therebetween. In the same way, the reflective filter and the light-receiving device can also be secured easily, while accurately defining the positional relationship therebetween. Consequently, in the second optical transmitter/receiver apparatus, the optical axis can be adjusted on the order of sub-microns through passive alignment.
In addition, since the second base supporting the body of the optical fiber can be secured to the package after the semiconductor laser device, supported by the first base secured to the package, has been subjected to an output test, the loss caused when an optical fiber is connected to a defective semiconductor laser device can be reduced.
In the first or second optical transmitter/receiver apparatus, the first base preferably includes optical-axis-direction positioning means for regulating a position of the one end of the optical fiber in an optical axis direction.
In such a case, it is possible to regulate the position of the one end of the optical fiber in the optical axis direction and the distance between the semiconductor laser device secured to the first base and the one end of the optical fiber. As a result, the coupling efficiency of the light emitted from the semiconductor laser device can be improved at the one end of the optical fiber.
In the first or second optical transmitter/receiver apparatus, the fiber end supporting means preferably includes on-vertical-plane positioning means for regulating a position of the one end of the optical fiber on a plane vertical to the optical axis.
In such a case, it is possible to regulate the position of the one end of the optical fiber on the plane vertical to the optical axis. As a result, the coupling efficiency of the light emitted from the semiconductor laser device can be improved at the one end of the optical fiber.
In the first or second optical transmitter/receiver apparatus, the on-vertical-plane positioning means preferably includes: a concave groove being formed in the fiber end supporting region of the first base so as to extend in an optical axis direction, having a pair of walls coming closer to each other in a direction from an opening to a bottom, and supporting the one end of the optical fiber; and a pressing member, secured over the concave groove of the first base, for pressing the one end of the optical fiber supported by the concave groove onto the pair of walls of the concave grooves.
In such a case, the one end of the optical fiber can be supported at three contact points, i.e., points on the pair of walls of the concave groove and on the pressing member. Thus, it is possible to accurately regulate the position of the one end of the optical fiber on the plane vertical to the optical axis.
In the first or second optical transmitter/receiver apparatus, the fiber end supporting means preferably includes: a concave groove, formed in the fiber end supporting region of the first base so as to extend in an optical axis direction, for supporting the one end of the optical fiber; and a resin-introducing groove, formed in the fiber end supporting region of the first base so as to extend in a direction intersecting the concave groove and to communicate with the concave groove, for introducing a supplied resin into the concave groove.
In such a case, since the resin can be introduced with certainty through the resin-introducing groove into the concave groove, the optical fiber can be secured to the concave groove with certainty.
In the first or second optical transmitter/receiver apparatus, the fiber end supporting means preferably includes: a concave groove, formed in the fiber end supporting region of the first base so as to extend in an optical axis direction, for supporting the one end of the optical fiber; and a resin-draining groove, formed in the fiber end supporting region of the first base so as to extend in a direction intersecting the concave groove and to communicate with the concave groove, for draining a resin supplied to the concave groove to the outside.
In such a case, the residual, redundant resin supplied to the concave groove and used for securing the optical fiber to the groove can be drained through the resin-draining groove to the outside. Thus, it is possible to prevent the overflowing resin from reaching the vicinity of the semiconductor laser device. As a result, the deterioration in characteristics of the semiconductor laser device can be prevented.
Preferably, the first or second optical transmitter/receiver apparatus further includes a reflective film, formed between the reflective filter and the light-receiving device, for reflecting the optical signal to be transmitted that has been emitted from the semiconductor laser device.
In such a case, it is possible to prevent the optical signal to be transmitted, which has been emitted from the semiconductor laser device, from being incident onto the light-receiving device. Thus, even when the light-receiving device is disposed in the vicinity of the semiconductor laser device, it is possible to prevent noise from being generated because of the optical signal to be transmitted.
Preferably, the first or second optical transmitter/receiver apparatus further includes: a wavelength selecting reflective filter, supported by being inserted into the body of the optical fiber and the second base at a position closer to the other end of the optical fiber than the reflective filter is, for transmitting the optical signal to be transmitted that has been emitted from the semiconductor laser device and for selectively reflecting an optical signal to be received on a predetermined wavelength band among a plurality of optical signals to be received on a plurality of wavelength bands, the optical signals having been incident through the other end of the optical fiber; and a second light-receiving device, secured to the second base, for receiving the optical signal to be received that has been reflected by the wavelength selecting reflective filter.
In such a case, the optical signal to be received on a predetermined wavelength band among a plurality of optical signals to be received on a plurality of wavelength bands, which have been incident through the other end of the optical fiber, is reflected by the wavelength selecting reflective filter. The reflected optical signal to be received on the predetermined wavelength band can be received by the second light-receiving device. Thus, a plurality of optical signals to be received on a plurality of wavelength bands, which have been transmitted from a center station, can be received separately.
In such an embodiment, it is more preferable to form a filter for selectively transmitting the optical signal to be received on the predetermined wavelength band between the wavelength selecting reflective filter and the second light-receiving device.
Then, it is possible to prevent noise from being generated from the optical signal to be transmitted and incident onto the second light-receiving device and from the optical signals to be received on the wavelength bands other than the predetermined wavelength band.
In the first or second optical transmitter/receiver apparatus, the semiconductor laser device is preferably secured to the first base such that an optical axis of light emitted from the semiconductor laser device is inclined with respect to an optical axis of the optical fiber by a predetermined tilt angle.
In such a case, the light emitted from the semiconductor laser device and reflected by the incident portion of the optical fiber is very less likely to be incident onto the active layer region of the semiconductor laser device again. Thus, sufficient return loss can be ensured.
In this embodiment, the predetermined tilt angle is preferably in the range from 2 to 3 degrees.
Then, sufficient return loss can be ensured and, at the same time, the decrease in coupling efficiency can be prevented.
In order to accomplish the first object, a third optical transmitter/receiver apparatus of the present invention includes: an optical fiber for transmitting an optical signal to be transmitted and receiving an optical signal to be received therethrough; a base including mutually spaced optical signal transmitting and receiving regions and a fiber end supporting region located between the optical signal transmitting and receiving regions; a semiconductor laser device, secured to the optical signal transmitting region of the base, for emitting the optical signal to be transmitted; optical-axis-direction positioning means, formed in the optical signal transmitting region of the base, for regulating a position of one end of the optical fiber in an optical axis direction, the optical signal to be transmitted that has been emitted from the semiconductor laser device being incident onto the one end; fiber end supporting means, formed in the fiber end supporting region of the base, for supporting the one end of the optical fiber, while regulating a position of the one end of the optical fiber on a plane vertical to the optical axis; fiber body supporting means, formed in the optical signal receiving region of the base, for supporting the body of the optical fiber; a reflective filter, supported by being inserted into the fiber body supporting means and the optical fiber, for transmitting the optical signal to be transmitted that has been emitted from the semiconductor laser device, and for reflecting the optical signal to be received that has been incident through the other end of the optical fiber; and a light-receiving device, secured to the optical signal receiving region of the base, for receiving the optical signal to be received that has been reflected by the reflective filter.
In the third optical transmitter/receiver apparatus, since the optical-axis-direction positioning means for regulating a position of one end of the optical fiber in an optical axis direction is formed in the optical signal transmitting region of the base, it is possible to regulate with certainty the position of the one end of the optical fiber in the optical axis direction and the distance between the semiconductor laser device secured to the first base and the one end of the optical fiber. In addition, since the fiber end supporting means for supporting the one end of the optical fiber, while regulating a position of the one end of the optical fiber on a plane vertical to the optical axis is formed in the fiber end supporting region of the base, it is possible to regulate with certainty the position of the one end of the optical fiber on the plane vertical to the optical axis.
Thus, in the third optical transmitter/receiver apparatus, it is possible to regulate the distance between the semiconductor laser device secured to the first base and the one end of the optical fiber and the position of the one end of the optical fiber on the plane vertical to the optical axis. As a result, the coupling efficiency of the light emitted from the semiconductor laser device can be improved at the one end of the optical fiber.
In the third optical transmitter/receiver apparatus, the fiber end supporting means preferably includes: a concave groove being formed in the base so as to extend in the optical axis direction, having a pair of walls coming closer to each other in a direction from an opening to a bottom, and supporting the optical fiber; and a pressing member, secured over the concave groove in the fiber end supporting region of the base, for pressing the one end of the optical fiber supported by the concave groove onto the pair of walls.
In such a case, the one end of the optical fiber can be supported at three contact points, i.e., points on the pair of walls of the concave groove and on the pressing member. Thus, it is possible to precisely regulate the position of the one end of the optical fiber on the plane vertical to the optical axis.
The method for fabricating an optical transmitter/receiver apparatus according to the present invention is provided for fabricating an optical transmitter/receiver apparatus including an optical fiber for transmitting an optical signal to be transmitted and receiving an optical signal to be received therethrough. The method includes the steps of: forming a optical fiber end supporting concave groove in a fiber end supporting region of a first base, the first base having mutually spaced optical signal transmitting and receiving regions and the fiber end supporting region located between the optical signal transmitting and receiving regions, the concave groove having such a cross-sectional shape as to support one end of the optical fiber and extending in an optical axis direction; securing a semiconductor laser device, emitting the optical signal to be transmitted, onto the optical signal transmitting region of the first base; forming an optical fiber body supporting concave groove in a second base, the optical fiber body supporting concave groove having such a cross-sectional shape as to support the body of the optical fiber and extending in the optical axis direction; securing the body of the optical fiber inside the optical fiber body supporting concave groove; forming a cut recess in the second base and the body of the optical fiber, the cut recess extending in a direction vertical to the optical axis; securing a reflective filter inside the cut recess, the reflective filter transmitting the optical signal to be transmitted that has been emitted from the semiconductor laser device and incident onto the one end of the optical fiber, and reflecting the optical signal to be received that has been incident through the other end of the optical fiber; securing a light-receiving device above the optical fiber body supporting concave groove in the second base, the light-receiving device receiving the optical signal to be received that has been reflected by the reflective filter; securing the one end of the optical fiber onto the optical fiber end supporting concave groove of the first base; and securing the second base onto the optical signal receiving region of the first base, the body of the optical fiber, the reflective filter and the light-receiving device having been secured to the second base.
In the method for fabricating an optical transmitter/receiver apparatus of the present invention, either one of the step of forming the optical fiber end supporting concave groove and the step of securing the laser may precede the other.
In accordance with the method for fabricating an optical transmitter/receiver apparatus of the present invention, the second base, onto which the body of the optical fiber, the reflective filter and the light-receiving device have already been secured, is secured to the first base. Thus, the second base may be secured to the first base after the first and second bases have been formed separately. Accordingly, the assembly process can be simplified as compared with a manufacturing method in which semiconductor laser device, one end and body of the optical fiber, reflective filter and light-receiving device are secured to a single base. Consequently, an optical transmitter/receiver apparatus, allowing for the adjustment of the optical axis on the order of sub-microns through passive alignment, can be fabricated more easily and accurately.
In this method, the cut recess extending in a direction vertical to the optical axis is formed in the second base and the body of the optical fiber secured to the optical fiber body supporting concave groove of the second base, and then the reflective filter is secured into the cut recess. Thus, the reflective filter can be secured to the optical path of the optical fiber with certainty.
The reflective filter is first secured to the second base and then the light-receiving device is secured over the optical fiber body supporting concave groove of the second base. Thus, the positional relationship between the reflective filter and the light-receiving device can be regulated precisely.
The semiconductor laser device is first secured to the first base and then one end of the optical fiber is secured to the optical fiber end supporting concave groove formed in the first base. Thus, the positional relationship between the semiconductor laser device and the one end of the optical fiber can also be regulated precisely.
In the method for fabricating an optical transmitter/receiver apparatus of the present invention, the step of securing the second base preferably includes the step of securing the second base onto the optical signal receiving region of the first base, while regulating a position of the one end of the optical fiber in the optical axis direction and a position of the optical fiber on a plane vertical to the optical axis.
In such a case, it is possible to regulate the distance between the semiconductor laser device secured to the first base and the one end of the optical fiber and the position of the one end of the optical fiber on the plane vertical to the optical axis. As a result, it is possible to fabricate an optical transmitter/receiver apparatus exhibiting excellent coupling efficiency of the light emitted from the semiconductor laser device at the one end of the optical fiber.
In the method for fabricating an optical transmitter/receiver apparatus of the present invention, the step of forming the concave groove preferably includes the step of forming a resin-introducing groove in the fiber end supporting region of the first base, the resin-introducing groove extending in a direction crossing the optical fiber end supporting concave groove and communicating with the optical fiber end supporting concave groove. The step of securing the one end of the optical fiber preferably includes the step of securing the one end of the optical fiber onto the optical fiber end supporting concave groove of the first base with a resin, the resin being supplied through the resin-introducing groove into the optical fiber end supporting concave groove.
In such a case, the resin can be introduced into the optical fiber end supporting concave groove with certainty. Thus, the optical fiber can be secured with certainty.
In order to accomplish the second object, a first optical semiconductor module of the present invention includes: a base including a concave groove extending in an optical axis direction and a cut recess extending in a direction vertical to the optical axis; a semiconductor laser device, secured to the base, for emitting semiconductor laser light; an optical fiber for transmitting the laser light emitted by the semiconductor laser device therethrough, the optical fiber being installed in the concave groove of the base with an incidence end face of the optical fiber in contact with a wall of the cut recess, the wall being closer to the semiconductor laser device; and an alignment mark, formed on the base, for aligning a position of the semiconductor laser device with a position of the base. The alignment mark is formed through the same photolithography and etching processes as processes applied to the concave groove.
In the first optical semiconductor module, the alignment mark is formed through the same photolithography and etching processes as those applied to the concave groove. Thus, since no positional misalignment is caused between the alignment mark and the concave groove that are both formed on the base, the positional misalignment between the semiconductor laser device positioned using the alignment mark and the optical fiber installed in the concave groove can be reduced to a large degree. As a result, the coupling efficiency of the laser light to the optical fiber can be improved.
In the first optical semiconductor module, the alignment mark preferably include a pair of side alignment marks, the side alignment marks being formed on both sides of a region of the base, to which region the semiconductor laser device is secured, so as to be symmetrically disposed with respect to the optical axis.
In such a case, the positional misalignment between the semiconductor laser device and the base in the direction vertical to the optical axis can be reduced within a plane parallel to the surface of the base. Thus, the positional misalignment between the laser light emitted from the semiconductor laser device and the optical fiber in the direction vertical to the optical axis can be reduced within a plane parallel to the surface of the base. As a result, the coupling efficiency of the laser light to the optical fiber can be increased to a large degree.
In the first optical semiconductor module, the alignment mark preferably includes a base edge alignment mark formed on an edge portion of the wall of the cut recess of the base, the wall being closer to the semiconductor laser device.
In such a case, since the positional misalignment between the semiconductor laser device and the base in the optical axis direction and the variation in distance between the emission end face of the semiconductor laser device and the incidence end face of the optical fiber can be reduced, the distance between the emission end face of the semiconductor laser device and the incidence end face of the optical fiber can be shortened. As a result, the coupling efficiency of the laser light to the optical fiber can be increased to a large degree.
In the first optical semiconductor module, the alignment mark preferably includes: a pair of side alignment marks, the side alignment marks being formed on both sides of a region of the base, to which region the semiconductor laser device is secured, so as to be symmetrically disposed with respect to the optical axis; and a base edge alignment mark formed on an edge portion of the wall of the cut recess of the base, the wall being closer to the semiconductor laser device.
In such a case, since the positional misalignment between the laser light emitted from the semiconductor laser device and the optical fiber in the direction vertical to the optical axis can be reduced within a plane parallel to the surface of the base. In addition, the variation in distance between the emission end face of the semiconductor laser device and the incidence end face of the optical fiber can also be reduced. As a result, the coupling efficiency of the laser light to the optical fiber can be increased to an even larger degree.
Preferably, the first optical semiconductor module further includes a laser edge alignment mark, formed on an edge portion of a bottom surface of the semiconductor laser device, for aligning a position of the semiconductor laser device with a position of the base, the edge portion of the bottom surface being closer to the optical fiber.
In such a case, since the positional misalignment between the semiconductor laser device and the base in the optical axis direction and the variation in distance between the emission end face of the semiconductor laser device and the incidence end face of the optical fiber can be reduced, the distance between the emission end face of the semiconductor laser device and the incidence end face of the optical fiber can be shortened. As a result, the coupling efficiency of the laser light to the optical fiber can be increased to a large degree.
In this embodiment, the alignment mark of the base preferably includes a base edge alignment mark formed on an edge portion of the wall of the cut recess of the base, the wall being closer to the semiconductor laser device.
In such a case, since the variation in distance between the emission end face of the semiconductor laser device and the incidence end face of the optical fiber can be further reduced, the distance between the emission end face of the semiconductor laser device and the incidence end face of the optical fiber can be further shortened. As a result, the coupling efficiency of the laser light to the optical fiber can be increased to an even larger degree.
In order to accomplish the second object, a second optical semiconductor module of the present invention includes: a base including a concave groove extending in a direction of an optical axis; a semiconductor laser device having a double channel structure, being secured to a base and emitting semiconductor laser light; an optical fiber, installed in the concave groove of the base, for transmitting the laser light emitted by the semiconductor laser device therethrough; and an alignment mark, formed on the base, for aligning a position of the semiconductor laser device with a position of the base. The alignment mark includes a convex alignment mark having a convex portion and existing between a pair of grooves each having a V-shaped cross section, the grooves being formed at positions symmetric to the optical axis in a region of the base, to which region the semiconductor laser device is secured.
In the second optical semiconductor module of the present invention, the alignment mark includes a convex alignment mark having a convex portion and existing between a pair of grooves each having a V-shaped cross section that are formed at positions symmetric to the optical axis on the base. Accordingly, the positional misalignment between the semiconductor laser device and the base in the direction vertical to the optical axis can be reduced within a plane parallel to the surface of the base. Thus, the positional misalignment between the laser light emitted from the semiconductor laser device and the optical fiber in the direction vertical to the optical axis can be reduced within a plane parallel to the surface of the base. As a result, the coupling efficiency of the laser light to the optical fiber can be increased to a large degree. In this case, since the semiconductor laser device has a double channel structure and no electrode needs to be formed in the region of the base in which the pair of grooves each having the V-shaped cross section are formed, the pair of grooves each having the V-shaped cross section can be formed.
In the second optical semiconductor module, the pair of grooves on both sides of the convex portion are formed through the same photolithography and etching processes as processes applied to the concave groove.
In such a case, since no positional misalignment is caused between the convex alignment mark and the concave groove, the positional misalignment between the semiconductor laser device located using the convex alignment mark and the optical fiber installed in the concave groove can be reduced to a large degree. As a result, the coupling efficiency of the laser light to the optical fiber can be considerably improved.